Stripper plate spring unit

ABSTRACT

A stripper plate spring unit for a punch or stamping press has a cup-like cap provided with a side wall extending upwardly from a bottom wall that has a central opening through it. Slidably disposed in this opening is the upper end of a vertical stem, from which stem-supporting means inside the cap extends laterally over the surrounding bottom wall of the cap. Spring-supporting means secured to the lower end of the stem extends laterally beneath the cap and is adapted to seat against a stripper plate. A coil spring encircles the stem and is compressed between the bottom of the cap and the top of the spring-supporting means to normally press the stem-supporting means tightly against the top of the bottom wall of the cap.

United States Patent Vecchi Au 26 1975 STRIPPER PLATE SPRING UNIT [75] Inventor: John Calisto Vecchi, Natrona Primary Exa'vmnerfiwllhe Abemromble orney, n zrmn, 1 Helghts Pa All Age t or F Brow Murray Fl ck &

Peckham [73] Assignee: Oberg Manufacturing Co., Inc., Freeport, Pa.

[57] ABSTRACT [22] Filed: Apr. 25, 1974 A str1pper plate sprmg unit for a punch or stamping [2]] App]. No.: 464,243 press has a cup-like cap provided with a side wall extending upwardly from a bottom wall that has a cen- 52] U S G 83/140. 83/133 tral opening through it. Slidably disposed in this open- [511 In} .Cl; B2,) 7/06 g is the pp end of a Vertical stem from which [58] i 6 133 143 stem-supporting means inside the cap extends laterally over the surrounding bottom wall of the cap. Spring- 5 6] References Cited supporting means secured to the lower end of the stem extends laterally beneath the cap and is adapted to UNITED STATES PATENTS seat againsta stripper plate. A coil spring encircles the SOkO-lOWSky tem and is compressed between the bottom of the 2,579'641 12/195 f' 83/140 cap and the top of the spring-supporting means to nor- :T mally press the stem-supporting means tightly against 3solgss 3,1970 il i 83/140 X the top of the bottom wall of the cap. 3,742.79? Vecch1 5 Claims 3 Drawing Figures 3,848,496 11/1974 Stevens ct al. v. 83/140 x I I3 I N ll 30 l I 20' l I I8 PATENTEB AUG 2 6 I975 STRIPPER PLATE SPRING UNIT 1 In punch preses and stamping presses, stripper plates are used to prevent the workpieces from being lifted off the bottom dies by the punches or stamping dies as they rise. When the tool holder is in its upper position, the stripper plate is supported a fixed distance below it by studs slidably mounted in the tool holder. While the work is being punched or stamped, the stripper plate engages the work and the springs are compressed by the downwardly moving tool holder. These springs hold the stripper plate against the work while the punches or upper stamping dies are being withdrawn from it.

For proper operation of the stripper plate, it is highly desirable that all of the springs be preloaded to a certain extent and that the preloading of all of the springs be the same. This has been difficult to do with the ordinary arrangement of stripper plate springs in a press.

It is among the objects of this invention to provide a stripper plate spring unit which can be quickly put in place or removed, which can be easily preloaded, which can readily be preloaded to the same extent as other spring units of the same construction, and the length of which can be changed without affecting the preloading.

The. preferred embodiment of the invention is illustrated in the accompanying drawings, in which FIG. 1 is a plan view of a die set;

FIG. 2 is an enlarged end view thereof with the die set open; and I FIG. 3 is a vertical section, taken on line III-III of FIG. 1, but showing the die set closed.

Referring to the drawings, a lower die holder 1 is rigidly mounted on a suitable base and supports a die 2 that may be provided with a plurality of vertical openings through it that are aligned with similar openings down through the holder for disposal of punchings when the die set is part of a punch press. If part of a stamping press, the die is shaped according to the work to be done. A die set for a punch press is shown in the drawings to illustrate the invention.

Spaced above the die holder is a tool holder 5, in this case a punch holder, that is supported in a punch press by conventional means (not shown) by which it can be reciprocated vertically to move it toward and away from the die holder. The punch holder carries punches 6 that extend down below it in alignment with the die openings. To guide the punch holder in its vertical movement, the upper ends of guide posts 7 are rigidly mounted in it, with the posts extending down into bearings in vertical passages in the bottom die holder.

Between the punch and die holders there is a floating stripper plate 10 secured to the lower ends of studs 1 1 that are encircled by sleeves 12 that engage the stripper plate and washers 13 on the studs in contact with their heads. The sleeves, washers and stud heads are slidably mounted in vertical passages through the punch holder. The sleeves ensure that the studs will hold the stripper plate parallel to the punch and die holders. When the die set is open; i.e., the punch holder is at the top of its stroke as shown in FIG. 2; the stripper plate is spaced above the die. The plate is provided with vertical guide passages 14, through which the guide posts 7 extend.

When the die set is closed, which means that punch holder 1 is at the bottom of its stroke as shown in FIG. 3, the stripper plate has been moved down into contact with the top of the workpiece 17, which stops further downward movement of the plate, but the punch holder continues down to cause the punches to punch the work. When the punch holder starts to move up again, expanding coil springs maintain the stripper plate tightly against the work until the punch holder engages washers 1 3 and lifts studs 11, whereby the workpiece is stripped from the punches. 1

It is a feature of this invention that the coil springs just mentioned form part of stripper plate spring units 18, which are so constructed that they all can be quickly and easily preloaded to the same extent in order that they will exert uniform pressure against the stripper plate when they press it down against the work. Accordingly, as shown in FIG. 3, each spring unit includes a cup-like cap 20, that has a central opening through its bottom wall. Slidably disposed in this opening is the upper end of a vertical stem 21 that is supported by means secured to it inside the cap and extending laterally from it over the surrounding bottom wall of the cap. Although the stem-supporting means could be a head on the stem, preferably it consists of a cap screw 22 extending down through a washer 23 and into a threaded bore in the upper end of the stem. The screw clamps the washer tightly against the top of the stern, and the washer overlies the bottom wall of the cap. The lower end of the stem likewise is provided with laterally extending means, preferably an integral head 24 when a cap screw and washer are mounted on the'upper end of the stem. Compressed between this head and the bottom of the cap is a coil spring 35 encircling the stem. This spring normally holds washer 23 down firmly on the bottom wall of the cap.

The spring units are mounted in place by providing the bottom of the punch holder with upwardly extending sockets 27 of uniform depth for snugly receiving the caps 20 of the units. With the tops of the caps engaging the upper walls of the sockets, the bottoms of the spring units lightly touch or nearly touch the top of the stripper plate. When the punch holder continues to move down after tlie stripper plate has engaged the workpiece, the coil springs are compressed as the caps slide down the stationary stems 21. As the punch holder rises again, the coil springs expand and hold the stripper plate down until the punches have been pulled out of the work. Then the studs 11 lift the stripper plate away from the workpiece.

When the punches require redressing, which shortens them, the sleeves 2 are ground off to shorten them the same amount, and the upper ends of caps 20 also are ground down to the same extent. Of course, this has no affect on the preloading of the spring units. Since with shorter caps the cap screws 22 will be closer to the upper ends of the caps, the upper walls of the punch holder sockets 27 are provided with recesses 30 that can receive the heads of the cap screws when the coil springs are compressed.

By making all of the stems of the spring units the same length, and by using springs that are the same length in their unstressed condition and have the same capacity, all of the spring units will be preloaded to the same extent when the cap screws are screwed down tightly against the stems. For example, the unstressed springs may be 2 inches long and the distance from the bottom of the caps to the top of the underlying springsupporting stem heads 1 13/16 inches. This would mean that all of the springs would be compressed 3/16 inch, so that the units are uniformly preloaded accordingly. No adjusting or checking of preload is required.

According to the provisions of the patent statutes, I have explained the principle of my invention and have illustrated and described what I now consider to represent its best embodiment. However, I desire to have it understood that, within the scope of the appended claims, the invention may be practiced otherwise than as specifically illustrated and described.

I claim:

1. A stripper plate preloaded spring unit for a press, comprising a cup-like cap having a side wall extending upwardly from a bottom wall provided with a central opening therethrough, a vertical stern below the cap and having an upper end slidably disposed in said opening, stem-supporting means inside said cap secured to the upper end of said stern and extending laterally therefrom over the surrounding bottom wall of the cap, spring-supporting means secured to the lower end of the stem and extending laterally therefrom beneath said cap and adapted to seat against a stripper plate, said stem holding said stem-supporting means and spring supporting means a fixed distance apart, and a coil spring encircling said stem and compressed between the bottom of said cap and the top of said springsupporting means, whereby the spring normally presses the stem-supporting means tightly against the top of the underlying bottom wall of the cap.

2. A stripper plate preloaded spring unit according to claim I, in which said stem supporting means and stem are screwed together, and said spring-supporting means is integral with the stem.

3. A stripper plate preloaded spring unit according to claim 1, in which said stem and spring-supporting means form an integral stud with an outwardly projecting head at its lower end, the upper end of the stud having a downwardly extending threaded axial bore therein, and said stem-supporting means including fastening means screwed into said bore, a portion of the fastening means inside the cap engaging the top of the stud.

4. A stripper plate preloaded spring unit according to claim 3, in which said fastening means include a cap screw screwed into said bore, and a washer held against the top of the stud by the screw and normally engaging the top of the bottom wall of the cap.

5. The combination with a press tool holder having a plurality of upwardly extending sockets of uniform depth in its bottom, a stripper plate below said holder and spaced therefrom, and means suspending the stripper plate from said tool holder, of a plurality of spring units disposed between said holder and plate, each of said units comprising a cup-like cap having a side wall extending upwardly from a bottom wall provided with a central opening therethrough, said cap being disposed in one of said sockets in engagement with the upper wall thereof, a vertical stem below the cap and having an upper end slidably disposed in said cap opening, stem-supporting means inside said cap secured to the upper end of said stem and extending laterally therefrom over the surrounding bottom wall of the cap, spring-supporting means secured to the lower end of the stern and extending laterally therefrom beneath said cap for engaging the top of said stripper plate, the lower surfaces of all of said spring-supporting means being the same distance from the bottoms of the overlying caps, and a coil spring encircling each stern and compressed between the bottom of the overlying cap and the top of the underlying spring-supporting means, all of said springs being preloaded to substantially the same extent, whereby the springs normally press all of the stem-supporting means tightly against the tops of the underlying bottom walls of said caps with substantially the same pressure. 

1. A stripper plate preloaded spring unit for a press, comprising a cup-like cap having a side wall extending upwardly from a bottom wall provided with a central opening therethrough, a vertical stem below the cap and having an upper end slidably disposed in said opening, stem-supporting means inside said cap secured to the upper end of said stem and extending laterally therefrom over the surrounding bottom wall of the cap, springsupporting means secured to the lower end of the stem and extending laterally therefrom beneath said cap and adapted to seat against a stripper plate, said stem holding said stemsupporting means and spring supporting means a fixed distance apart, and a coil spring encircling said stem and compressed between the bottom of said cap and the top of said springsupporting means, whereby the spring normally presses the stemsupporting means tightly against the top of the underlying bottom wall of the cap.
 2. A stripper plate preloaded spring unit according to claim 1, in which said stem supporting means and stem are screwed together, and said spring-supporting means is integral with the stem.
 3. A stripper plate preloaded spring unit according to claim 1, in which said stem and spring-supporting means form an integral stud with an outwardly projecting head at its lower end, the upper end of the stud having a downwardly extending threaded axial bore therein, and said stem-supporting means including fastening means screwed into said bore, a portion of the fastening means inside the cap engaging the top of the stud.
 4. A stripper plate preloaded spring unit according to claim 3, in which said fastening means include a cap screw screwed into said bore, and a washer held against the top of the stud by the screw and normally engaging the top of the bottom wall of the cap.
 5. The combination with a press tool holder having a plurality of upwardly extending sockets of uniform depth in its bottom, a stripper plate below said holder and spaced therefrom, and means suspending the stripper plate from said tool holder, of a plurality of spring units disposed between said holder and plate, each of said units comprising a cup-like cap having a side wall extending upwardly from a bottom wall provided with a central opening therethrough, said cap being disposed in one of said sockets in engagement with the upper wall thereof, a vertical stem below the cap and having an upper end slidably disposed in said cap opening, stem-supporting means inside said cap secured to the upper end of said stem and extending laterally therefrom over the surrounding bottom wall of the cap, spring-supporting means secured to the lower end of the stem and extending laterally therefrom beneath said cap for engaging the top of said stripper plate, the lower surfaces of all of said spring-supporting means being the same distance from the bottoms of the overlying caps, and a coil spring encircling each stem and compressed between the bottom of the overlying cap and the top of the underlying spring-supporting means, all of said springs being preloaded to substantially the same extent, whereby the springs normally press all of the stem-supporting means tightly against the tops of the underlyIng bottom walls of said caps with substantially the same pressure. 